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Hearing impairment, deafness, or hearing loss refers to the total or partial inability to hear sounds.

Symptoms may be mild, moderate, severe, or profound. A patient with a mild hearing impairment may have problems understanding speech, especially if there is a lot of noise around, while those with moderate deafness may need a hearing aid.

Some people are severely deaf and rely on lip-reading to communicate with others. People who are profoundly deaf can hear nothing at all and can find themselves totally reliant on lip-reading or sign language.

In the United States, around 15 percent of people over the age of 18 years report some level of hearing loss.

Causes

Hearing loss refers to either partial or total reduction in the ability to hear sounds.

The inner ear is home to some of the most delicate bones in the body, and damage to the eardrum or middle ear can cause hearing loss and deafness in a range of ways.

Hearing loss vs. deafness

It is important to distinguish between the different levels of hearing loss.

Hearing loss: This is a reduced ability to hear sounds in the same way as other people.

Deafness: This occurs when a person cannot understand speech through hearing, even when sound is amplified.

Profound deafness: This refers to a total lack of hearing. An individual with profound deafness is unable to detect sound at all.

The severity of hearing impairment is categorized by how much louder volumes need to be set at before they can detect a sound.

Some people define profoundly deaf and totally deaf in the same way, while others say that a diagnosis of profound deafness is the end of the hearing spectrum.

How does hearing work?

Sound waves enter the ear, move down the ear or auditory canal, and hit the eardrum, which vibrates. The vibrations from the eardrum pass to three bones known as the ossicles in the middle ear.

These ossicles amplify the vibrations, which are then picked up by small hair-like cells in the cochlea.

These move as the vibrations hit them, and the movement data is sent through the auditory nerve to the brain. The brain processes the data, which a person with functional hearing will interpret as sound.

Types

There are three different types of hearing loss:

1) Conductive hearing loss

This means that the vibrations are not passing through from the outer ear to the inner ear, specifically the cochlea. This type can occur for many reasons, including:

Ear infections can leave scar tissue, which might reduce eardrum function. The ossicles may become impaired as a result of infection, trauma, or fusing together in a condition known as ankylosis.

2) Sensorineural hearing loss

Hearing loss is caused by dysfunction of the inner ear, the cochlea, auditory nerve, or brain damage.

This kind of hearing loss is normally due to damaged hair cells in the cochlea. As humans grow older, hair cells lose some of their function, and hearing deteriorates.

Long-term exposure to loud noises, especially high-frequency sounds, is another common reason for hair cell damage. Damaged hair cells cannot be replaced. Currently, research is looking into using stem cells to grow new hair cells.

Sensorineural total deafness may occur as a result of congenital deformities, inner ear infections, or head trauma.

3) Mixed hearing loss

This is a combination of conductive and sensorineural hearing loss. Long-term ear infections can damage both the eardrum and the ossicles. Sometimes, surgical intervention may restore hearing, but it is not always effective.

Deafness and speech

Hearing loss can affect speech ability depending on when it occurs.

Prelingual deafness

This is an inability to fully or partially hear before learning how to utter or understand speech.

An individual with prelingual deafness was born with a congenital deformity or will have lost hearing during infancy.

In the majority of cases, people with prelingual deafness have hearing parents and siblings. Many are also born into families who did not already know sign language. They consequently also tend to have slow language development. The few who were born into signing families tend not to face delays in language development.

If children with prelingual deafness are given cochlear implants before the age of 4 years, they can acquire oral language successfully.

Oral language and the ability to use social cues are very closely interrelated. That is why children with hearing loss, especially those with severe symptoms, may not only experience delayed language development, but also slower social development.

As a result, children with prelingual deafness risk becoming socially isolated, unless they attend a school that has a well-run special needs department with other children who have the same condition.

Children who identify with a "deaf subculture," or those who have learned how to use sign language, might feel less isolated. However, some young people might experience isolation if their parents have not yet learned sign language.

There are cases of children with profound deafness who find themselves on the outer fringes of their hearing peers' social circles while not being fully accepted by peers with total deafness, due to a lack of fluency in sign language.

Post-lingual deafness

Most people with hearing loss have post-lingual deafness. They acquired spoken language before their hearing was diminished. A medication side effect, trauma, infection, or disease may have caused losing their sense of hearing.

In most people with post-lingual deafness, hearing loss onsets gradually.

Household members, friends, and teachers may have noticed a problem before they acknowledged the disability. Depending on the severity of hearing loss, the individual may have had to use hearing aids, receive a cochlear implant, or learn how to lip-read.

People who experience hearing loss face different challenges, depending on when it occurs and how long it takes to develop. They might have to become familiar with new equipment, undergo surgery, learn sign language and lip reading, and use various communication devices.

A feeling of isolation is a common problem, which can sometimes lead to depression and loneliness. A person with post-lingual hearing loss also has to face the often-distressing process of coming to terms with a disability. The condition may also pose challenges for household members, loved ones, and close friends, who have to adapt to the hearing loss.

Miscommunication can place a strain on relationships, not only for the person with the hearing impairment, but also the people around them. If the hearing loss is gradual and has not yet been diagnosed, family members may mistakenly believe that the individual with the condition is becoming more distant.

Unilateral and bilateral deafness

Single-sided deafness (SDD), or unilateral deafness, refers to hearing impairment in just one ear, while bilateral deafness is hearing impairment in both.

People with a unilateral hearing impairment may find it hard to carry on a conversation if the other person is on their affected side. Pinpointing the source of a sound may be more difficult, when compared with those who can hear well in both ears. Understanding what others are saying when there is a lot of environmental noise might be hard.

With little to no background noise, a person with unilateral deafness has virtually the same communicative abilities as a person with functional hearing in both ears.

Babies born with unilateral deafness tend to have developmental speech delays. They may find it harder to concentrate when they go to school. Social activities may be more challenging than it is for children with no hearing problems.

Symptoms

The symptoms of hearing impairment depend on its cause. Some people are born without being able to hear, while others suddenly become deaf due to an accident or illness. For most people, symptoms of deafness progress gradually over time.

Some conditions may have hearing loss as a symptom, such as tinnitus or stroke.

Hearing impairment in infants

The following signs may indicate a hearing problem:

Before the age of 4 months, the baby does not turn their head toward a noise.

By the age of 12 months, the baby still has not uttered a single word.

The infant does not appear to be startled by a loud noise.

The infant responds to you when they can see you, but respond far less or do not respond at all when you are out of sight and call out their name.

The infant only seems to be aware of certain sounds.

Hearing impairment in toddlers and children

These signs might become more evident in slightly older children:

The child is behind others the same age in oral communication.

The child keeps saying "What?" or "Pardon?"

The child talks in a very loud voice, and tends to produce louder-than-normal noises.

When the child speaks, their utterances are not clear.

Four levels of deafness

There are four levels of deafness or hearing impairment. These are:

Mild deafness or mild hearing impairment: The person can only detect sounds between 25 and 29 decibels (dB). They may find it hard to understand the words other people are saying, especially if there is a lot of background noise.

Moderate deafness or moderate hearing impairment: The person can only detect sounds between 40 and 69 dB. Following a conversation using hearing alone is very difficult without using a hearing aid.

Severe deafness: The person only hears sounds above 70 to 89 dB. A severely deaf person must either lip-read or use sign language in order to communicate, even if they have a hearing aid.

Profound deafness: Anybody who cannot hear a sound below 90dB has profound deafness. Some people with profound deafness cannot hear anything at all, at any decibel level. Communication is carried out using sign language, lip-reading, or reading and writing.

Diagnosis

Patients who suspect something is wrong with their hearing will initially go and see their doctor.

The doctor will talk to the patient and ask several questions regarding the symptoms, including when they started, whether or not they have gotten worse, and whether the individual is feeling pain alongside the hearing loss.

A physical examination

An otoscope is an instrument that allows a physician to examine the inside of the ear.

The doctor will look into the ear using an otoscope. This is an instrument with a light at the end. The following may be detected during the examination:

a blockage caused by a foreign object

a collapsed eardrum

an accumulation of earwax

an infection in the ear canal

an infection in the middle ear if a bulge is present in the eardrum.

cholesteatoma, a skin growth behind the eardrum in the middle ear.

fluid in the ear canal

a hole in the eardrum

The doctor will ask questions about the person's experiences with hearing, including:

Do you often find yourself asking people to repeat what they said?

Do you find it hard to understand people on the telephone?

Do you miss the doorbell when it rings? If so, does this happen frequently?

When you chat with people face-to-face, do you have to focus carefully?

Has anybody ever mentioned to you that you might have a problem with your hearing?

Do you find more people mumble today than they used to?

internal you hear a sound, do you often find it hard to determine where it is coming from?

When several people are talking, do you find it hard to understand what one of them is telling you?

Are you often told that the television, radio, or any sound-producing device is too loud?

Do you find male voices easier to understand than female voices?

Do you spend most of each day in a noisy environment?

Have you often found yourself misunderstanding what other people say to you?

Do you hear rushing, hissing, or ringing sounds?

Do you avoid group conversations?

If you answered "yes" to most of the above questions, see a doctor and have your hearing checked.

General screening test

A doctor may ask the patient to cover one ear and describe how well they hear words spoken at different volumes, as well as checking sensitivity to other sounds.

If the doctor suspects a hearing problem, they will probably be referred to either an ear, nose, and throat (ENT) specialist or an audiologist.

Further tests will be carried out, including:

A tuning fork test: This is also known as the Rinne test. A tuning fork is a metal instrument with two prongs that produces a sound when it is struck. Simple tuning fork tests may help the doctor detect whether there is any hearing loss, and where the problem is.

A tuning fork is vibrated and placed against the mastoid bone behind the ear. The patient is asked to indicate when they no longer hear any sound. The fork, which is still vibrating, is then placed 1 to 2 centimeters (cm) from the auditory canal. The patient is asked again whether they can hear the fork.

As air conduction is greater than bone conduction, the patient should be able to hear the vibration. If they cannot hear it at this point, it means that their bone conduction is superior to their air conduction.

This suggests a problem with sound waves getting to the cochlea through the ear canal.

Audiometer test: The patient wears earphones, and sounds are directed into one ear at a time. A range of sounds is presented to the patient at various tones. The patient has to signal each time a sound is heard.

Each tone is presented at various volumes, so that the audiologist can determine at which point the sound at that tone is no longer detected. The same test is carried out with words. The audiologist presents words at various tones and decibel levels to determine where the ability to hear stops.

Bone oscillator test: This is used to find out how well vibrations pass through the ossicles. A bone oscillator is placed against the mastoid. The aim is to gauge the function of the nerve that carries these signals to the brain.

Routine screening of children

The American Academy of Pediatrics (AAP) recommends that children have their hearing tests at the following times:

when they start school

at 6, 8, and 10 years of age

at least once when they are in middle school

once during high school

Testing newborns

The otoacoustic emissions (OAE) test involves inserting a small probe into the outer ear; it is usually done while the baby is asleep. The probe emits sounds and checks for "echo" sounds bouncing back from the ear.

If there is no echo, the baby might not necessarily have a hearing problem, but doctors will need to carry out further tests to make sure and to find out why

Treatment

Help is available for people with all types of hearing loss. Treatment depends on both the cause and severity of the deafness.

Sensorineural hearing loss is incurable. When the hair cells in the cochlea are damaged, they cannot be repaired. However, various treatments and strategies can help improve quality of life.

Hearing aids

Hearing aids can help to improve hearing and quality of life.

These are wearable devices that assist hearing.

There are several types of hearing aid. They come in a range of sizes, circuitries, and levels of power. Hearing aids do not cure deafness but amplify the sound that enters the ear so that the listener can hear more clearly.

Hearing aids consist of a battery, loudspeaker, amplifier, and microphone. Today, they are very small, discreet, and can fit inside the ear. Many modern versions can distinguish background noise from foreground sounds, such as speech.

A hearing aid is not suitable for a person with profound deafness.

The audiologist takes an impression of the ear to make sure the device fits well. It will be adjusted to suit auditory requirements.

Examples of hearing aids include:

Behind-the-ear (BTE) hearing aids: These consist of a dome called an earmold and a case, with a connection linking one to the other. The case sits behind the outer ear, with the connection to the dome coming down the front of the ear. The sound from the device is either electrically or acoustically routed to the ear.

BTE hearing aids tend to last longer than other devices, as the electrical components are located outside the ear, meaning that there is less moisture and earwax damage These devices are more popular with children who need a sturdy and easy-to-use device.

In-the-canal (ITC) hearing aids: These fill the outer part of the ear canal and can be seen. Soft ear inserts, usually made of silicone, are used to position the loudspeaker inside the ear. These devices fit most patients straight away and have better sound quality.

Completely in the canal (CIC) hearing aids: These are tiny, discreet devices but not recommended for people with severe hearing loss.

Bone conduction hearing aids: These assist people with conductive hearing loss, as well as those unable to wear conventional type hearing aids. The vibrating part of the device is held against the mastoid with a headband. The vibrations go through the mastoid bone, to the cochlea. These devices can be painful or uncomfortable if worn for too long.

Cochlear implants

If the eardrum and middle ear are functioning correctly, a person may benefit from a cochlear implant.

This thin electrode is inserted into the cochlea. It stimulates electricity through a tiny microprocessor placed under the skin behind the ear.

A cochlear implant is inserted to help patients whose hearing impairment is caused by hair cell damage in the cochlea. The implants usually improve speech comprehension. The latest cochlear implants have new technology that helps patients enjoy music, understand speech better even with background noise, and use their processors while they are swimming.

According to the National Institutes of Health (NIH), there were about 58,000 adults and 38,000 children with cochlear implants in the U.S. as of 2012. The World Health Organization (WHO) says approximately 219,000 people globally use one, most of them in industrial countries.

On the outside, a cochlear implant consists of:

A microphone: This gathers sound from the environment.

A speech processor: This prioritizes the sounds that matter more to the patient, such as speech. The electrical sound signals are split into channels and sent through a very thin wire to the transmitter.

A transmitter: This is a coil secured with a magnet. It is located behind the outer ear and transmits the processed sound signals to the internally implanted device.

On the inside:

A surgeon secures a receiver and stimulator in the bone beneath the skin. The signals are converted into electrical impulses and sent through internal wires to the electrodes.

Up to 22 electrodes are wound through the cochlea. The impulses are sent to the nerves in the lower passages of the cochlea and then directly to the brain. The number of electrodes depends on manufacturers of the implant.

Children will usually have cochlear implants in both ears, while adults tend to have just one.

Sign language and lip-reading

Sign language can help communication between people who are no longer able to hear.

Some people with hearing impairment may have speech problems, as well as difficulties in understanding speech from other people.

A high percentage of people with hearing impairment can learn other ways of communicating.

There is a range of sign languages that are, in some cases, wildly different to one another.

Lip reading

Also known as speechreading, lip reading is a method for understanding spoken language by watching the speaker's lip, facial and tongue movements, as well as extrapolating from the data provided by the context and any residual hearing the patient might have.

People who became hearing impaired after they learned to speak can pick up lip reading rapidly; this is not the case for those who are born hearing-impaired.

Sign language

This is a language that uses signs made with the hands, facial expressions, and body postures, but no sounds. It is used mainly by those who are deaf.

There are several different types of sign languages. British Sign Language (BSL) is very different from American Sign Language (ASL). For instance, BSL uses a two-handed alphabet, whereas American sign language uses a one-handed alphabet.

Some countries use the sign language introduced by missionaries from far away. Norwegian sign language, for example, is used in Madagascar.

Sign language is completely different from the spoken form, word order, and grammar in BSL is not the same as it is in spoken English. ASL is more grammatically similar to spoken Japanese than spoken English.

Prevention

Always wear earplugs if you spend long periods of time exposed to loud noise.

Nothing can prevent the hearing problems that occur from birth or hearing impairments due to illnesses or accidents.

However, some measures can be taken to reduce the risk of losing some of your sense of hearing.

The structures in the ears can be damaged in several different ways. Long-term exposure to noise above 85 dB – the volume of a typical lawnmower - can eventually cause hearing loss.

The following measures may help protect your hearing:

TV, radio, music players, and toys: Do not set the volume too high. Children are especially sensitive to the damaging effects of loud music. Noisy toys can put children's hearing at risk.

Headphones: Focus on isolating the sounds you want to hear and blocking out as much environmental sound as is possible, instead of drowning it out with high volume.

Occupational health: If you work in a noisy environment, such as discos, nightclubs, and pubs, wear earplugs or earmuffs.

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